The present invention relates to an apparatus and a process for fixing a bow-shaped member or brace made from wire and used for correcting misalignments of teeth in humans. In the apparatus, a brace is inserted in holding plates or brackets, of which each bracket is fixed to the labial or lingual surface of the teeth and is fixed by a ligature wire using a tool to the holding plates, as well as to the ligature wire.
In orthodontology the use of a wire brace for correcting misalignments of teeth in a so-called band brace apparatus is a known process. For this purpose brackets are fixed to the labial or lingual surface of the teeth and in same is formed a lock, in which the wire brace can be inserted. In order that the force of the brace be transferred to the teeth, it is necessary to fix the brace to the brackets. This fixing can be achieved in many different ways, e.g. by rubber rings or fine wires, the latter fastening being referred to as a ligature.
The application and fixing of such a wire brace is relatively complicated, particularly if it is necessary to correct teeth in both upper and lower jawbones.
The ligatures are formed from fine wires with a thickness of a few tenths of a millimeter, e.g. 0.2 to 0.3 mm, which are placed round the brackets and whose ends are twisted for stretching the wire. The ligature wire is placed over the brace and extends below two flaps arranged on the brackets, so that it cannot be stripped off. Fixing generally takes place with a needle holder, in which is secured a ligature wire.
A twister is known (Japanese Utility Model 1 373 903), which simplifies the application and tensioning of the ligature wires on the brackets. The twister is constructed as a rod-shaped member, on whose one end are mounted two jaws, of which one jaw is displaceable. On sliding back the one jaw, a pin is exposed, over which is placed a ligature wire in the form of a closed loop and onto which is again advanced the slid back jaw. The loop can now be placed over the bracket and the twister is manually turned until the ligature wire engages snugly on the bracket. It is then possible to slide back the jaw again and the twisted end of the loop can be removed from the pin.
In this known appliance it is necessary to obtain the twisting by turning the appliance manually. Experience has shown that roughly fifteen turns are required for a ligature, this quantity being dependent on the size of the bracket and the nature of the preshaping of the ligature wire. This relatively large number of turns involves a considerable amount of time and a large amount of physical effort.